What would cause a knocking sound you can hear on the inside of my 2015 Kia Sportage, but not on the outside? It happens once in awhile, but the noise seems to stop when I turn on the AC.

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your Sportage. A knocking sound inside the vehicle that stops when the AC is turned on could indicate an issue with the blend door actuator in your HVAC system. The actuator controls airflow by adjusting the position of internal doors, and when it malfunctions, it can produce a knocking or tapping noise. This usually happens when the actuator's gears become worn, or the motor fails intermittently. The noise stops when the AC is turned on, which could be because the blend door moves to a different position and no longer tries to adjust, temporarily silencing the issue. Since the problem is happening more frequently, it's worth inspecting the actuator and related components before they worsen or fail completely. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!